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What kind of problems will occur if input voltage is higher than 0.5V?

Latest Updated:09/29/2006

Question:

(Reset)   Power-on reset conditions described in the user's manual and datasheet include the following: "Make sure that the reset input voltage is 0.5V when a power source voltage passes 2.5V (Note 1)."
What kinds of problems will occur if input voltage is higher than 0.5V? In my current application, the voltage goes over 0.5V momentarily. [2006/09/29]

Answer:

Reset conditions specify that, "If the RESET pin is returned to "H" level after being held at "L" level for 2μs (Note2) or more, reset is released." In addition, "L" input voltage specifications for the RESET pin are 0V (min.) to 0.2Vcc (max.) [V]. Therefore, when the power source voltage Vcc is 2.5V as described above, it is necessary to set the reset input voltage to 0.5V or less (0.5V = 0.2 x 2.5V). If this condition is not satisfied, "L" level input to the RESET pin will not be satisfied, and reset may not occur properly.

Note 1: Vcc varies depending on the MCU. The above description is based on the assumption that the minimum value of the operating voltage Vcc is [2.5V] and the maximum value (0.2Vcc) of the "L" input voltage VIL for reset is [0.5V]. "L" input voltage specifications for the RESET pin may vary between MCUs, so please check the electrical characteristics in the datasheets.

Note 2: This value differs according to the MCU as follows:

  • 2μs: 3822A, 3823, 3826A, 38C1, 38C2A, 38D2, 38C5, 38D5, 38C8, 7540, 7542, 7544, 7560A
  • 16 XIN cycles: 3803, 3803H, 3804, 3804H, 3886
  • 20 XIN cycles: 3850A, 3851, 3858, 7516

(#104851)

Suitable Products
3803H
3803L
3823
3850A
3858
38D2
38D5
7544
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